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Physics Procedia

Out-of-equilibrium behavior of coarsening ferromagnets

Michel Pleimling

Published Jan 1, 2010• 0 citations
Publisher

Abstract

The out-of-equilibrium properties of ferromagnets quenched below the critical point are discussed in the dynamical scaling limit. The autoresponse and the autocorrelation are studied for both perfect and disordered ferromagnets. The scaling functions of the autoresponse are found to be in agreement with the predictions coming from the theory of local scale-invariance. Large finite time corrections to the scaling behavior of the autocorrelation are revealed for the disordered magnets.

DOI
10.1016/j.phpro.2010.09.048

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We study dynamic fluctuations in non-disordered finite dimensional ferromagnetic systems quenched to the critical point and the low temperature phase. We investigate the fluctuations of two two-time quantities, called χ and C , the averages of which yield the self-linear response and correlation functions. We introduce a restricted average of the χs, summing over all configurations with a given value of C . We find that the restricted average ⟨χ⟩ C obeys a scaling form, and that the slope of the scaling function approaches the universal value of the limiting effective temperature in the long time limit and for . Our results tend to confirm the expectation that time-reparameterization invariance is not realized in coarsening systems at criticality. Finally, we discuss possible experimental tests of our proposal.
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Motivated by recent numerical findings of Henkel et al (2006 J. Phys. A: Math. Gen. 39 L589) we re-examine via Monte Carlo simulations the linear response function of the two-dimensional Ising model with Glauber dynamics quenched to the critical point. At variance with the results of Henkel et al , we detect discrepancies between the actual scaling behavior of the response function and the prediction of local scale invariance. Such differences are clearly visible in the impulse autoresponse function, whereas they are drastically reduced in the integrated response functions. Accordingly, the scaling form predicted on the basis of local scale invariance simply provides an accurate fitting form for some quantities but cannot be considered to be exact.